The MMU, or memory management unit, is a component that provides the CPU with its primary interface to a computer's memory. The MMU serves a number of functions designed to facilitate both enhanced security and to simplify memory interaction for programmers.
Virtual and Physical Address Translation
In some systems, the MMU handles the conversion from the virtual memory addresses handled by the CPU to the physical addresses of memory in the hardware.
Virtual Address Space
The MMU and a supporting operating system may use virtual address spaces as a form of security by giving each running program an isolated section of memory in which to run.
In addition to security, virtual addresses are used as a form of hardware abstraction to make the use of virtual memory as transparent as possible to programmers.
To balance the cost of high speed memory and the time spent by the CPU waiting for memory output, a number of caches of varying sizes and speeds exist. On most systems, at least a few of these caches are coordinated by the MMU.
Communication between different components of a system occurs over a set of wires called the system bus. Since all devices must use the same bus, and simultaneous transmission is impossible, the MMU works to arbitrate access to the system bus.
- Photo Credit "The Cup of Yes and No (RAM)" is Copyrighted by Flickr user: dailyinvention (Stefan) under the Creative Commons Attribution license.
Processor Speed Vs. Memory
Processor speed and memory are two common ways to measure the overall power or quality of a computer. Both very different, they...